466 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



the oscular valves ; interradial spaces broad near margin, narrowing 

 at the middle of r to about 3 to 5 mm., this narrow area separating 

 the prominent paxillar spines of adjacent areas to within 5 mm. of 

 the oscular valves. This narrow area is abundantly supplied with 

 small spiracles to a point a little short of the middle of R, where 

 begin a series of irregular, bandlike, dark-brown spiracular areas 

 extending upon the grayish lateral membrane from the margin of 

 the paxillar area, these forming a series, of which the fourth, fifth, 

 and sixth from the inner end are the longest and extend nearly or 

 quite to the interradial line. They are 12 to 15 mm. long, accord- 

 ing to tension of actinolateral membrane. The lateral membrane 

 adjacent to the paxillar area is colored browm. Supradorsal mem- 

 brane very thin and transparent between the numerous conspicuous 

 criss-crossing muscle bands, the interspaces provided with from 1 to 6 

 conspicuous spiracula. Pseudopaxillae in 7 rows along each ray. 

 The outermost row consists of paxillae of conspicuous size, with 

 pedicel 3 mm. long and 4 (sometimes 3) slender unequal spinelet?>, 

 the longest 8 mm., the shortest 3 mm. The next row (toward the 

 median line) consists of very much smaller paxillae, with pedicel 

 about 0.5 mm. high, or less, and about 3 spinelets (or less) 2.5 mm. 

 high. These paxillae are in a transverse line with the outermost. 

 The paxillae of the next row alternate with these and with the 

 median radial. Both the median and aclradial are rudimentary, 

 with 1 to 3 sessile spinelets from 0,5 to 1.5 mm. long, so that the 

 supradorsal membrane rests upon the ambulacral ridge. The paxil- 

 lae have 4 long, slender lobes, forming in the delicate dorsal integu- 

 ment a calcareous network with irregular meshes along the lateral 

 regions and irregular rhomboidal meshes along the median area. 

 The supradorsal membrane is raised at numerous points by the 

 paxillar spinelets, from which the very definite branching muscle- 

 bands radiate. Osculum prominent, the valves with 8 or 10 spines; 

 about 4 spines belonging to the same paxilla radiate toward the. 

 end of the ray, the membrane between their tips and the base of the 

 valves having numerous spiracula. The width of the real ray, 

 omitting the supradorsal membrane, is only about 10 mm. at the 

 base. 



Ambulacral furrows narrow; tube feet large in 2 series. Fur- 

 row spinelets 3, flattened at the base and tapering to a point, the 

 adoral slightly the longest (1.5 to 1.75 mm.). Each spinelet is 

 capped by a narrow sacculus of variable length, but usually short. 

 Aperture papilla very broadly obovate, about as long as the longest 

 furrow spinelet. The calcareous part is slightly shorter than the 

 longest spinelet as the papilla is bordered by a flange of tissue. 



Armature of mouth plates very similar to that of pullatus; 4 mar- 

 ginal spines (the innermost not always spaced from the other 3) and 



